The present invention relates to plastic fittings for joining sections of plastic tubing, and, more particularly, to plastic fittings that provide an indication of achieving a certain torque level upon the tightening of the fitting.
Numerous industries use metallic tubes and fittings of copper, stainless steel, and steel where connection of high strength and integrity are needed. Metallic plumbing is very suitable in many applications. However, in certain industries, the fluids conveyed may attack metal components and the metal can contaminate the conveyed fluids, i.e., the semiconductor processing industry. Highly inert fluoropolymers may be utilized for the fittings, tubing, and components in such applications, for example, polytetrafluoroethylene (PTFE), and perfluoroalkoloxy (PFA). To maintain a clean and non-hazardous environment, it is essential that the fittings provided for coupling to sections of tubing are not easily unintentionally disconnected and that the tubing/fitting interface maintains its integrity even under mechanical stress. Various types of fittings are known in the art for these purposes.
One standard type of fitting, known as a FLARETEK(copyright) fitting, available from the assignee of this application, provides for a fitting body, with an elongate nose with a tapered or rounded tip, and a fitting nut that is attachable thereto. A section of tubing is placed with a nut thereon in engagement with the elongate nose section and the fitting nut is rotated and drawn onto the fitting body, pinching the flared tubing end between the nut and the fitting body. Although fluoropolymer fittings are very robust and have excellent performance characteristics, for many applications they are not as hard as traditional metal fittings and not as common. Thus, particularly for an infrequent user, providing the proper tightening torque is problematic. Over tightening of the fitting nut to the fitting body may damage the fitting nut, tubing, and/or fitting body. For example, threads may be stripped under substantially less torque than in similarly sized metal fittings. The damage may not be detected until materials are flowing through the various tubing sections and a potentially hazardous leak occurs. Under torqueing can fail to provide an adequate fluid seal and mechanical connection.
Thus, there is a need for a fluid flow fitting that provides a fitting assembler with notification that the fitting nut has been sufficiently tightened so that an optimum seal and mechanical connection has been created between fitting body, tubing end, and fitting nut. This notification may be visual, audible, and/or by touch means providing an instant and easily identifiable warning.
The needs described above are met by the torque confirmation fitting of the present invention. The torque confirmation fitting is used for coupling to a tubing end having a fluid flow duct and generally includes a fitting body, a fitting nut, and a torque confirmation means. In a preferred embodiment, the fitting body has a nose section that receives a flared end of the tubing. The torque confirmation means has a collar portion and one or more prongs. The fitting nut is rotatably joinable to the fitting body and cooperates with the torque confirmation portion. The end of the tubing with the nut and the torque confirmation thereon is engaged with the fitting body. The fitting nut is then rotatably joined to the fitting body and in doing so engages the torque confirmation portion. The continued tightening of the fitting nut to the fitting body, in the preferred embodiments, causes the prong of the torque confirmation portion to provide a visual indication that the fitting nut has been sufficiently and/or optimally tightened to the fitting body.